On the surface of cellular tissue responding to the stimulation of sympathetic nerve, the adrenergic receptor exists. This receptor is divided into two types, i.e. .alpha. and .beta.. The reaction via .alpha.-receptor is generally excitation, and causes the contraction of a smooth muscle and vessel.
On the other hand, the response of heart caused by the stimulation of .beta..sub.1 -receptor is the excitation such as the increase of heart rate, contraction and automaticity. The stimulation of .beta..sub.2 -receptor causes the relaxation of smooth muscle, e.g. tracheal, intestinal, uterine smooth muscle, etc. and the dilation of vessel.
Accordingly, the selective blockade of .beta..sub.1 -receptor acts on the heart depressedly, and gives physiological changes, for example, the decrease of heart rate, contraction, automaticity and stroke volume. Such pharmacological properties show that .beta..sub.1 -receptor blockers are useful for the treatment of diseases which need the utmost decrease of myocardial oxygen demand, i.e. angina pectoris, myocardial infarction, congestive heart failure, hypertension, arrhythmia, etc.